1. Field of the Invention
The present invention relates to a plug connector with plug contacts which are connected to electric wires, a connector which includes this plug connector and an associated receptacle connector mounted on a board, and portable terminal equipment which includes such a connector.
2. Description of the Prior Art
Some surface-mount components (e.g., speakers, microphones and vibration motors) of cellular phones, PDAs (personal digital assistants) and other portable devices are not compatible with reflow soldering which is performed after being temporarily soldered to a circuit board, and therefore cannot be mounted directly to a circuit board.
Accordingly, it is generally the case that receptacle connectors are mounted on (are soldered to) a circuit board, such surface-mount components are connected to plug connectors via electric wires (cables), and the plug connectors are connected to the receptacles.
This type of connector structure is disclosed in Japanese Unexamined Patent Publication No. 2004-55485 (hereinafter referred to as Patent Document 1).
Specifically, the receptacle connector disclosed in Patent Document 1 includes a receptacle insulator with a recessed portion, and two receptacle contacts 132 which are mounted on a circuit board to be fixed thereto so as to face the inner wall and the side surface of the receptacle insulator, respectively. The plug connector includes a plug insulator and two plug contacts and two electric wires (cables), wherein the plug insulator which has dimensions allowing the plug insulator to be completely accommodated in the recessed portion of the receptacle insulator, the two plug contacts are fixed to the plug insulator, and one end of each of the two electric wires is connected to the two plug contacts, respectively, while the other end of each of the two electric wires is connected to the aforementioned surface-mount component.
Therefore, if the plug insulator is fitted into the recessed portion of the receptacle insulator, the plug insulator is completely accommodated in the recessed portion while each plug contact and the associated receptacle contact come into contact with each other, so that the aforementioned circuit board and the electric wires are electrically connected to each other.
In the connector disclosed in Patent Document 1, it is difficult for the plug connector to be provided with more than two electrodes (i.e., more than two plug contacts) since the two plug contacts are fixed to opposite side portions of the plug insulator, respectively. Additionally, it is also difficult for the receptacle connector to be provided with more than two electrodes (i.e., more than two receptacle contacts) since the two receptacle contacts are separated in the lengthwise direction of the receptacle insulator so as to face each other. Supposing that the receptacle connector is designed so that it contains more than two electrodes (i.e., more than two receptacle contacts), e.g., four electrodes which are arranged at regular intervals in the direction of arrangement of the electric wires, the receptacle insulator increases in size in the direction of alignment of the receptacle contacts, so that the plug insulator also increases in size.
In addition, only one side of each plug contact comes in contact with the associated receptacle contact (namely, each receptacle contact comes in contact with the associated plug contact only from one side of the associated plug contact), and accordingly, it is difficult to maintain a stable contacting state between each plug contact and the associated receptacle contact in the case where an external force, which may be produced when the electric wires bend, vibrate or are stretched by cable laying, is exerted on the plug contacts.
It becomes especially difficult to maintain such a stable contacting state when the two electric wires W bend/flex in the direction of arrangement thereof. Namely, in this particular case, the receptacle insulator which receives a force from the electric wires is biased in the direction of arrangement of the electric wires, and accordingly, the contact pressure between one of the two plug contacts and the associated receptacle contact increases while the other plug contact and the associated receptacle contact decreases. Namely, the contact resistance between each plug contact and the associated receptacle contact easily fluctuates due to an external force exerted on the electric wires, so that it tended to be difficult to stabilize the electrical characteristics of the connector and to reduce the difference in the electrical characteristics between the electric wires.